The development and initial psychometric evaluation of a measure assessing adherence to prescribed exercise: the Exercise Adherence Rating Scale (EARS)

Abstract

Objectives

There is no gold standard for measuring adherence to prescribed home exercise. Self-report diaries are commonly used however lack of standardisation, inaccurate recall and self-presentation bias limit their validity. A valid and reliable tool to assess exercise adherence behaviour is required. Consequently, this article reports the development and psychometric evaluation of the Exercise Adherence Rating Scale (EARS).

Design

Development of a questionnaire.

Setting

Secondary care in physiotherapy departments of three hospitals.

Participants

A focus group consisting of 8 patients with chronic low back pain (CLBP) and 2 physiotherapists was conducted to generate qualitative data. Following on from this, a convenience sample of 224 people with CLBP completed the initial 16-item EARS for purposes of subsequent validity and reliability analyses.

Methods

Construct validity was explored using exploratory factor analysis and item response theory. Test-retest reliability was assessed 3 weeks later in a sub-sample of patients.

Results

An item pool consisting of 6 items was found suitable for factor analysis. Examination of the scale structure of these 6 items revealed a one factor solution explaining a total of 71% of the variance in adherence to exercise. The six items formed a unidimensional scale that showed good measurement properties, including acceptable internal consistency and high test-retest reliability.

Conclusions

The EARS enables the measurement of adherence to prescribed home exercise. This may facilitate the evaluation of interventions promoting self-management for both the prevention and treatment of chronic conditions.

Introduction

Exercise recommendations for adults with chronic conditions vary depending on the patients’ physical condition, the intensity and progression of their illness, and any co-morbidity [1]. Self-management involves collaboration between the patient and their healthcare provider (HCP), allowing patients to manage and monitor their health and any difficulties that arise [2]. Long-term adherence to these programmes is important for patients to maintain lasting benefits [3]. However, evidence demonstrates that levels of adherence to prescribed exercise are often low, limiting benefits that could be gained [4], [5], [6], [7].

Exercise is widely recognised as necessary for primary and secondary prevention, and treatment of chronic illness [8]. Thus, it is of vital importance that adherence to prescribed exercise is adequately assessed. Measurement of adherence is complex and there is no gold standard for measuring adherence to prescribed home exercise [9], [10]. Recent systematic reviews investigating adherence to prescribed exercise in musculoskeletal populations [11] and a chronic low back pain (CLBP) population [5], found self-report diaries to be the most common measure of adherence. However, there is no standardised diary that can be used across research studies, meaning results are not easily comparable between studies. In addition, poor completion rates for diaries, together with inaccurate recall and self-presentation bias, may further affect validity of this data [12]. Electronic devices such as accelerometers and pedometers can be used to assess adherence [13], but these require the patient to use them systematically, and therefore might only be successful for more adherent patients. Furthermore, electronic devices do not capture specific prescribed exercises [14]. Moreover, using electronic devices has been shown to increase exercise, leading to difficulties obtaining an accurate baseline measure of adherence [15].

The development of a valid measure is a priority as this may provide a better understanding of adherence to prescribed home exercise [5], [8], [16]. Additionally, it may provide a quick and simple way to assess adherence and an indication of reasons for non-adherence. Such information could aid the development of effective interventions that encourage long-term self-management of chronic conditions. This study reports the development and initial psychometric evaluation of the first measure to assess adherence to prescribed home exercise: the Exercise Adherence Rating Scale (EARS).